Correlation of spin states and spin delocalization with the dioxygen reactivity of catecholatoiron(III) complexes
Correlation of spin states and spin delocalization with the dioxygen reactivity of catecholatoiron(III) complexes
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DOI：
10.1021/ic051173y
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发表时间：
2005-11-28
影响因子：
4.6
通讯作者：
Funabiki, T
中科院分区：
文献类型：
--
作者：
Higuchi, M;Hitomi, Y;Funabiki, T
一系列邻苯二酚铁（III）配合物[（FeL）-L-III（4Cl-cat）] BPh 4（L =（4-MeO）（2）TPA（1），TPA（2），（4-Cl）（2）TPA（3），（4-NO2）TPA（4），（4-NO2）（2）TPA（5）; TPA = tris（吡啶-2-基甲基）胺; 4Cl-cat = 4-氯儿茶酚），已经通过磁化率测量和EPR，H-1 NMR，和UV-vis-NIR光谱来阐明邻苯二酚配体上的自旋离域与O-2反应性的相关性以及O-2反应性的自旋状态依赖性。在123 K的冷冻CH 3CN的EPR谱清楚地表明，吸电子基团的引入有效地将自旋平衡从高自旋转移到低自旋状态。在243 K时，用Evans方法测定了5的有效磁矩，结果表明，5含有36%的低自旋物种，而1-4主要处于高自旋状态.顺磁性H-1 NMR位移的自旋离域的4Cl-猫配体的评价显示，semiquinonatoiron（II）字符是更显着的低自旋物种比在高自旋物种。的反应速率常数的对数是线性相关的儿茶酚铁（III）和semiquinonatoiron（II）的高自旋配合物1-3的状态之间的能隙，虽然配合物4和5偏离负线性。低自旋复合物的较低的反应性，尽管其较高的自旋密度的儿茶酚配体相比，高自旋类似物，表明参与的铁（111）中心，而不是儿茶酚配体，在与O-2的反应。
A series of catecholatoiron(III) complexes, [(FeL)-L-III(4Cl-cat)]BPh4 (L = (4-MeO)(2)TPA (1), TPA (2), (4-Cl)(2)TPA (3), (4-NO2)TPA (4), (4-NO2)(2)TPA (5); TPA = tris(pyridin-2-ylmethyl)amine; 4Cl-cat = 4-chlorocatecholate), have been characterized by magnetic susceptibility measurements and EPR, H-1 NMR, and UV-vis-NIR spectroscopies to clarify the correlation of the spin delocalization on the catecholate ligand with the O-2 reactivity as well as the spin-state dependence of the O-2 reactivity. EPR spectra in frozen CH3CN at 123 K clearly showed that introduction of electron-withdrawing groups effectively shifts the spin equilibrium from a high-spin to a low-spin state. The effective magnetic moments determined by the Evans method in a CH3CN solution showed that 5 contains 36% of low-spin species at 243 K, while 1-4 are predominantly in a high-spin state. Evaluation of spin delocalization on the 4Cl-cat ligand by paramagnetic H-1 NMR shifts revealed that the semiquinonatoiron(II) character is more significant in the low-spin species than in the high-spin species. The logarithm of the reaction rate constant is linearly correlated with the energy gap between the catecholatoiron(III) and semiquinonatoiron(II) states for the high-spin complexes 1-3, although complexes 4 and 5 deviate negatively from linearity. The lower reactivity of the low-spin complex, despite its higher spin density on the catecholate ligand compared with the high-spin analogues, suggests the involvement of the iron(111) center, rather than the catecholate ligand, in the reaction with O-2.